Yes, here is their policy.
Our SMTP relay service is provided to
you as part of your email account. As
such, you must set up the service when
you configure your email account
settings. Your email account includes
250 SMTP relays per mailbox per day.
This limit resets once each day,
approximately every 24 hours between
10P.M. and 5 A.M., Arizona Time. If
you need more than 250 relays for your
mailbox, you can purchase additional
relay packs (in packs of 50). You can
use a maximum of 500 SMTP relays per
day, per email account. If you want to
use more than 500 relays per day, you
can distribute SMTP relays across
multiple email accounts.